Continuous extrusion under the large expansion ratio is an advanced forming process for manufacturing copper strip, preventing mould structure, die structure, expansion chamber structure and the shape of the billet section is important process paraments of deformation. Based on the characteristic of the forming process, the model of rigid-plastic FEM on DEFORM-3D is established and the numerical simulation of continuous extrusion forming process of the copper strip is carried. The metal flow regularity and the mean-square deviation of velocity with the different process paraments is analyzed. As the result, when using the drum form of preventing mould with promote flow angle and the die with variable calibrating strap, the mean-square deviation of velocity is 0.58. When the second extending angle is 134°, the mean-square deviation of velocity is 0.23. When size of billet is 30 x 1.64 mm2, the mean-square deviation of velocity is only 0.19.